I recently returned from a fishing trip with my son and brothers. This combination of campers and anglers had not been previously tried, and I am happy to say we didn’t come up empty handed. Eating fresh caught trout was a true privilege and delight, but as a biochemistry major, it got me thinking. How did freshwater fish stack up against the likes of ocean dwellers for their nutritional content, specifically in essential fatty acids (EFAs)? When I interview new patients, I find they are now commonly using “fish oil” for general health, it is recommended by nutritionists and physicians, and available on most grocery store shelves.
Oils and fats are essentially the same thing, though they are generally classified fat or oil based on their state at room temperature (oils are liquid and fats are solid). The caloric value is exactly the same, and the body can create many of the oil-based compounds needed to make the body work from other fat and oil sorces in the diet (including cholesterol, which is a whole other blog!). However, a class of oils called EFAs are just that – essential, to be consumed and used in their original state because we cannot manufacture them through regular body processes.
The two fractions we need are called omega-3 and omega-6. Omega-3 is formally known as linoleic acid (LA), with derivatives called GLA and AA. Omega-6 is chemically alpha-linolenic acid (ALA), with derivatives EPA and DHA. These initials are provided in case you are shopping and wonder what they are talking about. Theoretically, only LA and ALA are absolutely essential. However, the fatty acids derived from them are also generally considered essential and included in much of the research that guides our use of them.
EFA deficiency has been identified in many diseases including mental disorders, diabetes, atherosclerosis, hypertension, eczema, PMS, immune dysfunction, and inflammatory conditions such as rheumatoid arthritis. In inflammation, EFAs have been seen to regulate the immune response and diminish joint destruction.
Here are some of the best sources to get the EFAs you need. Depending on what you eat, you may not need to supplement.
LA is present in many vegetables and most vegetable oils – sunflower (65-75%), safflower (79%), evening primrose seed (72%), corn (57%), peanut (31%), canola (19-26%), and olive (8%) — which is why we usually recommend cold-pressed safflower oil and avoid the cheap canola oil. LA is abundant in the food supply and thus there is no need to supplement. GLA: The richest sources of GLA are borage (starflower) oil (20-24%); evening primrose oil (8-10%); and black currant oil (15-17%). GLA is present in small amounts in human breast milk and some foods, but the typical diet provides very little GLA. AA: Found in high amounts in eggs, fish and meat, AA is abundant in the food supply and supplementation is not usually necessary.
ALA is found in flax seed (18-22%) and flax seed oil (50-60%), and in small amounts in some nuts, green leafy vegetables, canola, wheat germ and black current seeds. EPA and DHA: EPA and DHA are found in fatty fish like salmon, mackerel and tuna. Depending on the source, fish oils vary in the amount of EPA and DHA they provide. Fish oil supplements often contain 18% EPA and 12% DHA, with more concentrated oils containing 30% EPA and 20% DHA. Algal sources of EPA and DHA are also widely available.
While dietary minimum requirements have not been established by the FDA, their recommended daily adequate intake for adults is defined as 4.44 grams of LA (omega-3); 2.22 grams of ALA (omega-6); and 0.65 grams of DHA/EPA combined. This ratio is considered optimal, so look to frequently include the best oils from plant sources in your cooking and baking.
Back to my trout. A study by the University of Quebec published in the American Journal of Clinical Nutrition found that those eating saltwater fish known for their increased fatty content (salmon, tuna, herring and sardines) had increased blood levels of omega-3s and -6s. They also found increased blood levels of mercury associated with eating these fish, but did not identify wild-caught versus farmed varieties. The leaner freshwater fish, while healthy in many ways and spared the mercury risk, did not contribute to the EFA levels in the participants’ blood levels. Hmm.
Concerned about mercury? These fish have a very low risk of mercury contamination: wild-caught Alaskan and Pacific Coast salmon, along with Pacific scallops, shrimp, oysters, clams, mussels, herring, and anchovies. Experts recommend this category for several meals per week. As you can see, two types of salmon (wild-caught Alaska salmon and wild-caught Pacific salmon) are included in this very low risk category. Low-risk ocean products would include canned light tuna, Pacific cod, Pacific haddock, wild-caught Atlantic salmon, mahi mahi, fresh/frozen Pacific tuna and Dungeness crab.
Conclusion? Continue to base your diet in vegetables, with weekly use of meats, eggs, and fish (once or twice). If your supply of fish isn’t identified as wild or fresh caught, ask. Wild salmon has one-third of the saturated fat of farm-fed, so half-the calories, and yet only marginally less EFAs. And stick to “Best Coast” fish and shellfish for the least risk of heavy-metal contamination. Or join me in a trout feast – and supplement!